1. Technical Field
The present invention relates to an illumination device and a projector.
2. Related Art
In general, projectors are each provided with an illumination device having a light source device that emits an illumination light beam, a liquid crystal light modulation device that modulates the illumination light beam from the illumination device (the light source device) in accordance with image information, and a projection optical system that projects the light modulated by the liquid crystal light modulation device on a projection surface such as a screen (see e.g., WO2004/20898).
The light source device has an ellipsoidal reflector and a light emitting tube having an emission center at the first focal point of the ellipsoidal reflector, and emits the light beam having the illumination light axis as the center axis thereof. Further, between the light source device and the area to be illuminated, there is disposed a concave lens, thus it is arranged to emit the light from the ellipsoidal reflector towards the posterior stage of the light path.
Incidentally, in association with downsizing of projectors in recent years, the demand of reducing the thicknesses of illumination devices has risen.